How To Overwinter Herbs

December 1, 2012

Perennial herb gardens come back each spring with very little effort on the gardener’s part. Hardy perennials like tarragon and lavender die back in winter. Prune them down to last year’s growth. Put a 2-3 in. layer of mulch on top to protect roots and to prevent heaving out of the soil with freezing and thawing. Onions and garlic (considered herbs by many, even though they’re actually bulbs) do well with either straw mulch or row covers.

For a supply of fresh mint through the fall months, cut off the top of the plant, put the roots in seed trays (or deeper boxes) and cover with soil. Keep in the greenhouse or cold frame.

Extend the growing season of annual herbs by bringing them indoors before the first frost. You can grow herbs like rosemary, chives or parsley inside your home in winter on a sunny windowsill. Herbs will also keep in the basement or garage if there is a small window for light.

Herbs do best if they have 5-6 hours of sun a day. Potted herb plants can be placed on tables or on the floor near any sunny window. Don’t put saucers under the potsthey don’t like wet feet! Generally, don’t water more often than once a week in winter. It’s best to water herbs in the morning. Use a spray bottle and mist lightly to maintain some humidity in the air, especially if your home has forced air heat. Use warm water. Check soil moisture regularly to prevent herbs from drying out completely.

Fertilizer is generally not needed for herbs over the ‘dormant’ winter months.

Use 8 to 12 in. diameter pots to allow roots plenty of growing room. Also, only use pots or containers with good drainage holes, but make sure the holes are partially blocked with cheesecloth or gravel to prevent soil from leaking out when you water. Fill pots about 3/4 full with a mix of compost and quality potting soil. Group several pots close to each other so there is plenty of moist air from the leaves being crowded together. Placing potted herb plants in a gravel-lined tray prevents root rot.

Before bringing any plants indoors, check for bugs and pull off any dead leaves. Cut back any scraggly growth. Allow plants to sit a week or two in a covered porch or garage before moving them into the house, so they can adapt gradually to changes in light, temperature and moisture.

To enjoy your herbs in recipes or for therapeutic needs, simply snip leaves as needed, and the plants should continue to grow and replenish throughout the chilly months.

They could be brought inside and wintered over, but both are pretty tricky to keep. They need to have good light: a sunny southern window or artificial lights work well. Both plants need to have good air circulation, and no drafts. Make sure they are potted in well-drained soil. Temperatures should average in the 60s. Be sure to not overwater them during the winter months, but do provide ample humidity around the plants by either misting them or by placing them on a tray of pebbles with water. A mudroom is a great environment for plants.

For Rosemary, try the varieties ‘Arp’ or ‘Hill Hardy’. For Lavender, look for varieties of Lavandula angustifolia, such as ‘Mundstead’ or some of the crosses with L. dentata such as Goodwin Greek Grey.